Melanin Biopolymers in Pharmacology and Medicine-Skin Pigmentation Disorders, Implications for Drug Action, Adverse Effects and Therapy

Melanins are biopolymeric pigments formed by a multi-step oxidation process of tyrosine in highly specialized cells called melanocytes. Melanin pigments are mainly found in the skin, iris, hair follicles, and inner ear. The photoprotective properties of melanin biopolymers have been linked to their perinuclear localization to protect DNA, but their ability to scavenge metal ions and antioxidant properties has also been noted. Interactions between drugs and melanins are of clinical relevance. The formation of drug-melanin complexes can affect both the efficacy of pharmacotherapy and the occurrence of adverse effects such as phototoxic reactions and discoloration. Because the amount and type of melanin synthesized in the body is subject to multifactorial regulation-determined by both internal factors such as genetic predisposition, inflammation, and hormonal balance and external factors such as contact with allergens or exposure to UV radiation-different effects on the melanogenesis process can be observed. These factors can directly influence skin pigmentation disorders, resulting in hypopigmentation or hyperpigmentation of a genetic or acquired nature. In this review, we will present information on melanocyte biology, melanogenesis, and the multifactorial influence of melanin on pharmacological parameters during pharmacotherapy. In addition, the types of skin color disorders, with special emphasis on the process of their development, symptoms, and methods of treatment, are presented in this article.

Janus kinase inhibitors and the changing landscape of vitiligo management: a scoping review

Vitiligo is a chronic skin condition caused by an autoimmune response that results in the progressive loss of melanocytes and recent studies have suggested that Janus kinase inhibitors (JAKi) are emerging as a promising new treatment modality. Therefore, to assess and understand the extent of knowledge in the emerging field of JAKi use in vitiligo, a scoping review of the literature was undertaken. The reviewed articles explored a wide variety of JAKi administered either orally or topically for vitiligo. There were no injectable JAKi studied. Tofacitinib was the most commonly studied oral JAKi in 16 of the 35 studies selected for review, followed by baricitinib (n = 3), and one study each with ritlecitinib, ruxolitinib, and upadacitinib. Ruxolitinib (n = 6) and tofacitinib (n = 6) were the most often studied topical JAKi, followed by delgocitinib (n = 1). Potential benefits may vary between JAKi based on their receptor selectivity profile and coexistent autoimmune diseases. A topical JAKi would be advantageous in limited body area involvement and in adolescents. Concurrent use of JAKi with phototherapy or sun exposure appears beneficial. Most studies permitted the use of other topical agents. Acne-related events, though frequent yet mild, were reported with both oral and topical JAKi. Nasopharyngitis, upper respiratory tract infections, and headaches were the most common adverse effects seen in the larger trials with JAKi. No serious or clinically meaningful hematology or thromboembolic events were detected. Treatment of vitiligo with oral or topical JAKi seems to be promising and the growing evidence shows a favorable risk-benefit profile.

Morphological characteristics of facial scars: A retrospective analysis according to scar location, onset, age, and cause

The morphology of facial scars shows a wide variation in terms of texture and colour. To date, there are no reliable predictors of aberrant scarring. We conducted a retrospective analysis to identify factors associated with specific scar features and types. Photographs and medical records of 428 patients with facial scars were retrospectively reviewed. Patients with keloids were excluded. The mean age of the patients was 45.43 ± 23.13 years with a male-to-female ratio of 1:1.36. Atrophic scars were the most common (42.8%), followed by flat scars (38.7%) and hypertrophic scars (18.5%). Scars on the forehead were more likely to be atrophic, whereas scars on the chin/jaw and around the mouth were more likely to be hypertrophic. Hypopigmentation was significantly more common in scars located on the forehead. Redness (erythema) was significantly more common in scars located on the chin/jaw. Old scars were less likely to be erythematous, and hypertrophic. Atrophic scars were more common in younger patients. Scars caused by dermatologic conditions, such as acne, were more likely to be atrophic, whereas surgical scars had the lowest risk of being atrophic or hypertrophic. In conclusion, the location, onset, and cause of facial scars were associated with specific features of scars.

Non-surgical treatment of post-burn hypopigmentation: a literature review

The treatment of post-burn hypopigmentation was primarily surgical before the advent of new technologies. Medical devices and therapies are emerging to manage scar sequelae that can be disfiguring and associated with severe psychosocial impact. These innovations have been poorly investigated for hypopigmentation, but they represent a real hope. We reviewed all articles published on Pubmed up to June 2022. Included studies had to specifically focus on treating post-burn hypopigmented scars. All articles evaluating transient solutions such as make-up, and articles describing inflammation-linked hypopigmentation with no etiological details or no burn injury history were excluded. Through this review, we have highlighted six different types of non-surgical treatments reported in post-burn leukoderma potentially allowing definitive results. Electrophoto-Biomodulation or E light (combining intensive pulsed light, radiofrequency, and cooling), topical daylight psoralen UVA therapy, and lasers (Fractional lasers using pulse energies or CO2FL devices, lasers-assisted drug delivery as local bimatoprost and tretinoin or pimecrolimus) have been explored with encouraging results in hypopigmented burns. Finally, other promising medical strategies include using FK506, a nonsteroidal anti-inflammatory drug, to induce melanogenesis or using melanocyte-stimulating hormones with fractional laser-assisted drug deliveries, which are expected to emerge soon.

Lichen Striatus: An Updated Review

BACKGROUND

Lichen striatus is a benign dermatosis that affects mainly children. This condition mimics many other dermatoses.

OBJECTIVE

The purpose of this article is to familiarize pediatricians with the clinical manifestations of lichen striatus to avoid misdiagnosis, unnecessary investigations, unnecessary referrals, and mismanagement of lichen striatus.

METHODS

A search was conducted in June 2023 in PubMed Clinical Queries using the key term "Lichen striatus". The search strategy included all observational studies, clinical trials, and reviews published within the past ten years. Only papers published in the English literature were included in this review. The information retrieved from the above search was used in the compilation of this article.

RESULTS

Lichen striatus is a benign self-limited T-cell mediated dermatosis characterized by a linear inflammatory papular eruption seen primarily in children. The onset is usually sudden with minimal or absent symptomatology. The eruption in typical lichen striatus consists of discrete, skin- colored, pink, erythematous, or violaceous, flat-topped, slightly elevated, smooth or scaly papules that coalesce to form a dull red, potentially scaly, interrupted or continuous band over days to weeks. Although any part of the body may be involved, the extremities are the sites of predilection. Typically, the rash is solitary, unilateral, and follows Blaschko lines. In dark-skinned individuals, the skin lesions may be hypopigmented at onset. Nails may be affected alone or, more commonly, along with the skin lesions of lichen striatus. The differential diagnoses of lichen striatus are many and the salient features of other conditions are highlighted in the text.

CONCLUSION

Lichen striatus is a self-limited condition that often resolves within one year without residual scarring but may have transient post-inflammatory hypopigmentation or hyperpigmentation. As such, treatment may not be necessary. For patients who desire treatment for cosmesis or for the symptomatic treatment of pruritus, a low- to mid-potency topical corticosteroid or a topical immunomodulator can be used. A fading cream can be used for post-inflammatory hyperpigmentation.

Insights from a joint pediatric dermatology-gynecology vulvar clinic: A retrospective study

BACKGROUND/OBJECTIVES

Pediatric vulvar disease has not been widely explored in the medical literature. Few studies focus on vulvar disease in skin of color. The vulvar disease can be distressing for young patients given the sensitive location, and providers may lack experience in diagnosing and managing vulvar dermatoses. We sought to characterize the conditions seen, diagnostic challenges encountered, and the racial and ethnic factors associated with vulvar diseases in our multidisciplinary pediatric dermatology-gynecology vulvar clinic at Children's National.

METHODS

Medical records of 220 patients who presented to our multidisciplinary pediatric dermatology-gynecology clinic were reviewed retrospectively.

RESULTS

Lichen sclerosus (LS) (36%, n = 80), inflammatory vulvitis (11%, n = 23), and vitiligo (9%, n = 19) were the three most frequent conditions observed. These conditions were often misdiagnosed as one another. There was a mean delay in diagnosis after symptom onset in LS patients of 16.43 months.

CONCLUSIONS

LS, inflammatory vulvitis, and vitiligo are common vulvar diseases among pediatric patients. Accurate diagnosis is important because LS must be treated aggressively to prevent sequelae. Further studies are warranted to help differentiate LS and vitiligo with consideration of skin tone.

Management of Severe Neutropenia in a Child With Chediak-Higashi Syndrome Using Granulocyte-Colony Stimulating Factor (G-CSF): A Case Report

Chediak-Higashi syndrome (CHS) is a congenital immunodeficiency disorder characterized by recurrent bacterial infections, oculocutaneous albinism, and abnormal intracellular protein transport. The incidence of CHS is rare, with approximately 500 cases reported so far. One of the key immunological features of CHS is neutropenia. The management of CHS includes supportive treatment, chemotherapy, methylprednisolone, IL-2 administration, and hematopoietic stem cell transplantation (HSCT). However, neutropenia can persist even after these treatments. This case report presents the successful management of severe neutropenia in an 8-year-old girl diagnosed with CHS. The patient exhibited classic CHS features, including hypopigmentation and recurrent infections. Initial treatment with antibiotics led to the resolution of the fever, but severe neutropenia persisted. Granulocyte-colony stimulating factor (G-CSF) therapy was initiated, which resulted in a substantial increase in the absolute neutrophil count (ANC) with no adverse effects. Throughout treatment with G-CSF, the patient remained stable. The patient was finally referred to the tertiary care center for consideration of bone marrow transplantation. This case highlights the potential safety and efficacy of G-CSF in managing CHS-associated neutropenia.

Observation of a Possible Successful Treatment of DEPDC5-Related Epilepsy with mTOR Inhibitor

The mechanistic target of the rapamycin signaling pathway serves as a central regulator of cell metabolism, growth, proliferation, and survival. In its regulation, the GTPase-activating protein activity toward Rags1 complex has an inhibitory effect. Mutations in genes encoding this complex protein are among the most common abnormalities in focal epilepsies. Within these mutations, the mutations affecting the DEPDC5 gene have been associated with different autosomal dominantly inherited epilepsy types. Due to the limited data available on mTOR inhibitor therapy in nontuberous sclerosis complex epileptic patients, here we present the clinical management of a patient with intractable epilepsy, skin hypopigmentation, and a DEPDC5 variant. The patient's phenotype is compatible with a nonlesional DEPDC5-related epileptic encephalopathy. We initiated compassionate, off-label everolimus treatment as the patient's condition continuously deteriorated. Due to bilateral pneumonia occurring at the beginning of the treatment, it was temporarily discontinued, and resumed in half the dose. Follow-up examination after 18 months showed a 90% reduction in seizure frequency with moderate improvement in attention function and nutritional status. Our case report emphasizes the importance of early genetic testing in patients with epileptic encephalopathy. Clinical consequences of mammalian target of rapamycin complex 1 (mTORC1) upregulation may be amenable to tailored treatment with mTOR inhibitors. A clinical trial on an international scale would be needed to draw conclusions.

Real-World Clinical Characteristics, Management, and Outcomes of 44 Paediatric Patients with Hypopigmented Mycosis Fungoides

Hypopigmented mycosis fungoides is a rare form of mycosis fungoides that is characterized by achromic lesions, early onset of disease, a predilection for darker skinned populations, and a predominance of CD8+ T cells. Due to the rarity and heterogeneous presentation of hypopigmented mycosis fungoides, there are no criteria that clearly define the clinical characteristics and treatment regimens for this condition. This retrospective study of 44 paediatric patients with hypopigmented mycosis fungoides aimed to summarize their epidemiological and clinical characteristics and assess the effectiveness and safety of different treatment regimens. Clinical manifestations were further classified into 3 morphological groups: hypopigmented lesions, papules overlying hypopigmented lesions, and erythematous plaques overlying hypopigmented lesions. In addition, the results of this study suggest that interferon alpha might be an effective and well-tolerated therapy that could shorten the treatment time to complete response compared with other treatments. Maintenance therapy and long-term follow-up reduced the recurrence rate.

Halo Phenomenon in Lobular Capillary Hemangioma: A Case Report of a Pyogenic Granuloma With Surrounding Cutaneous Hypopigmentation and Review of Tumors With Halo Phenomenon

A halo phenomenon describes a skin neoplasm that is surrounded by a hypopigmented or white halo. Halo lesions have been observed in association with an epithelial neoplasm (seborrheic keratosis), a fibrous lesion (surgical scar), a keratinocyte malignancy (basal cell carcinoma), melanocytic neoplasms, and vascular lesions. Benign lesions (café au lait macules and nevi) and malignant tumors (primary and metastatic melanoma) are melanocytic neoplasms that have developed perilesional halos. Halo nevi are a commonly occurring manifestation of a halo phenomenon; however, perilesional hypopigmented halos have also been observed around nevi in patients following treatment with antineoplastic drugs, acquisition of COVID-19 (infection and vaccine), the occurrence of a visceral tumor (including not only melanoma, but also papillary thyroid carcinoma and neuroendocrine cancer of the lung), surgery (such as the excision of a primary melanoma), and Turner syndrome. A halo phenomenon has also been observed in patients with congenital (capillary malformation-arteriovenous malformation and congenital hemangioma) or acquired (angioma, eruptive pseudoangiomatosis, infantile hemangioma, and lobular capillary hemangioma) vascular lesions. In summary, a halo phenomenon can occur in association with primary lesions of various embryologic derivations. Most commonly, they have been observed in around nevi and vascular tumors. Halo lobular capillary hemangioma can be added to the list of acquired vascular lesions with the potential to develop a halo phenomenon. The preservation of melanocytes with loss of melanin pigment expression in the reported patient suggests the possibility that a post-inflammatory etiology may be responsible for the genesis of her halo lobular capillary hemangioma.

Griscelli Syndrome With Hemophagocytic Lymphohistiocytosis: A Rare Case Report

Griscelli syndrome type 2 (GS2) is a rare, autosomal recessive condition caused by a mutation of the RAB27A gene that causes primary immunodeficiency and pigmentary dilution of skin and hair. It is a rare occurrence, with only 160 cases reported all over the world. It commonly progresses to hemophagocytic lymphohistiocytosis (HLH) due to immunodeficiency. We herein represent the case of a seven-month-old male child, the firstborn of a third-degree consanguineous marriage, who presented with recurrent viral infections and silvery grey hair. A definitive diagnosis of GS 2 was made in accordance with the pathognomonic appearance of hair on microscopic examination and whole genome sequencing, which revealed a homozygous missense mutation in exon 3 of the RAB27A gene. This article is being reported to highlight the rare incidence of this disease, its overlapping clinical features with malnutrition, the challenges faced in diagnosis, and the treatment modalities for it.

Haplotype-based analysis resolves missing heritability in oculocutaneous albinism type 1B

Oculocutaneous albinism (OCA) is a rare disorder of pigment production. Affected individuals have variably decreased global pigmentation and visual-developmental changes that lead to low vision. OCA is notable for significant missing heritability, particularly among individuals with residual pigmentation. Tyrosinase (TYR) is the rate-limiting enzyme in melanin pigment biosynthesis and mutations that decrease enzyme function are one of the most common causes of OCA. We present the analysis of high-depth short-read TYR sequencing data for a cohort of 352 OCA probands, ∼50% of whom were previously sequenced without yielding a definitive diagnostic result. Our analysis identified 66 TYR single-nucleotide variants (SNVs) and small insertion/deletions (indels), 3 structural variants, and a rare haplotype comprised of two common frequency variants (p.Ser192Tyr and p.Arg402Gln) in cis-orientation, present in 149/352 OCA probands. We further describe a detailed analysis of the disease-causing haplotype, p.[Ser192Tyr; Arg402Gln] ("cis-YQ"). Haplotype analysis suggests that the cis-YQ allele arose by recombination and that multiple cis-YQ haplotypes are segregating in OCA-affected individuals and control populations. The cis-YQ allele is the most common disease-causing allele in our cohort, representing 19.1% (57/298) of TYR pathogenic alleles in individuals with type 1 (TYR-associated) OCA. Finally, among the 66 TYR variants, we found several additional alleles defined by a cis-oriented combination of minor, potentially hypomorph-producing alleles at common variant sites plus a second, rare pathogenic variant. Together, these results suggest that identification of phased variants for the full TYR locus are required for an exhaustive assessment for potentially disease-causing alleles.

Skin Pigmentation Types, Causes and Treatment-A Review

Human skin pigmentation and melanin synthesis are incredibly variable, and are impacted by genetics, UV exposure, and some drugs. Patients' physical appearance, psychological health, and social functioning are all impacted by a sizable number of skin conditions that cause pigmentary abnormalities. Hyperpigmentation, where pigment appears to overflow, and hypopigmentation, where pigment is reduced, are the two major classifications of skin pigmentation. Albinism, melasma, vitiligo, Addison's disease, and post-inflammatory hyperpigmentation, which can be brought on by eczema, acne vulgaris, and drug interactions, are the most common skin pigmentation disorders in clinical practice. Anti-inflammatory medications, antioxidants, and medications that inhibit tyrosinase, which prevents the production of melanin, are all possible treatments for pigmentation problems. Skin pigmentation can be treated orally and topically with medications, herbal remedies, and cosmetic products, but a doctor should always be consulted before beginning any new medicine or treatment plan. This review article explores the numerous types of pigmentation problems, their causes, and treatments, as well as the 25 plants, 4 marine species, and 17 topical and oral medications now on the market that have been clinically tested to treat skin diseases.

6-Methylcoumarin Promotes Melanogenesis through the PKA/CREB, MAPK, AKT/PI3K, and GSK3β/β-Catenin Signaling Pathways

We investigated the effects of four coumarin derivatives, namely, 6-methylcoumarin, 7-methylcoumarin, 4-hydroxy-6-methylcoumarin, and 4-hydroxy-7-methylcoumarin, which have similar structures on melanogenesis in a murine melanoma cell line from a C57BL/6J mouse called B16F10. Our results showed that only 6-methylcoumarin significantly increased the melanin synthesis in a concentration-dependent manner. In addition, the tyrosinase, TRP-1, TRP-2, and MITF protein levels were found to significantly increase in response to 6-methylcoumarin in a concentration-dependent manner. To elucidate the molecular mechanism whereby 6-methylcoumarin-induced melanogenesis influences the melanogenesis-related protein expression and melanogenesis-regulating protein activation, we further assessed the B16F10 cells. The inhibition of the ERK, Akt, and CREB phosphorylation, and conversely, the increased p38, JNK, and PKA phosphorylation activated the melanin synthesis via MITF upregulation, which ultimately led to increased melanin synthesis. Accordingly, 6-methylcoumarin increased the p38, JNK, and PKA phosphorylation in the B16F10 cells, whereas it decreased the phosphorylated ERK, Akt, and CREB expressions. In addition, the 6-methylcoumarin activated GSK3β and β-catenin phosphorylation and reduced the β-catenin protein level. These results suggest that 6-methylcoumarin stimulates melanogenesis through the GSK3β/β-catenin signal pathway, thereby affecting the pigmentation process. Finally, we tested the safety of 6-methylcoumarin for topical applications using a primary human skin irritation test on the normal skin of 31 healthy volunteers. We found that 6-methylcoumarin did not cause any adverse effects at concentrations of 125 and 250 μM. Our findings indicate that 6-methylcoumarin may be an effective pigmentation stimulator for use in cosmetics and the medical treatment of photoprotection and hypopigmentation disorders.

Usage of Dermoscopy as an Effective Diagnostic Tool in Pityriasis Alba: A Prospective Observational Study Among Children in a Suburban Hospital in South India

BACKGROUND

Hypopigmented patches in patients with skin of color are usually a cause of concern. Pityriasis alba is a common skin condition that causes visible patches of hypopigmentation in children and adolescents. In addition to the cosmetic impairment, parents are concerned about the diagnosis of vitiligo and leprosy which also cause hypopigmented patches and have negative social implications. Dermoscopy is a useful diagnostic aid that is acquiring prominence in diagnosing a variety of skin diseases. Few studies exist that validate the use of dermoscopy as an effective tool in the diagnosis of Pityriasis alba.

OBJECTIVE

To evaluate the effectiveness of dermoscopy by correlating the clinical features of Pityriasis alba with dermoscopic images.

METHODS

Hypopigmented patches in 16 patients that were clinically diagnosed as Pityriasis alba were examined with a DermLite DL200 Hybrid dermoscope (Dermlite, CA, USA). All the dermoscopic images were photographically recorded and the findings were noted and correlated with the clinical stages of the disease.

RESULTS

Out of the 40 patches examined in 16 patients, dermoscopic images of white structureless spots, scaling, indistinct borders and normally pigmented hairs were consistently present in all the patches to propose these as the four dermoscopic criteria for the diagnosis of Pityriasis alba. Areas of light brown pigmentation, 17 (42.5%), erythema, 3 (7.5%), and faint pigmented network,11 (27.5%) were the other features noted in some of the patches.

CONCLUSION

In an ethnic South Indian population where the skin color is predominantly brown, hypopigmented patches are visibly obvious and concerning. Pityriasis alba, Pityriasis versicolor, Vitiligo, Nevus depigmentosus, and Leprosy are the five common conditions seen among children of which Pityriasis alba is the most prevalent. Offering the right diagnosis is essential for the correct management as well as excluding more serious conditions such as leprosy and vitiligo. In this study, Dermoscopy provided a valuable diagnostic aid in achieving this objective.

Does immune dysregulation contribute towards development of hypopigmentation in Indian post kala-azar dermal leishmaniasis?

Post kala-azar dermal leishmaniasis (PKDL), a sequel of apparently cured visceral leishmaniasis (VL) presents with papulonodular (polymorphic) or hypopigmented lesions (macular) and is the proposed disease reservoir. As hypopigmentation appears consistently in PKDL, especially the macular form, this study aimed to delineate immune factors that singly or in combination could contribute towards this hypopigmentation. At lesional sites, the presence of melanocytes and CD8⁺ T-cells was assessed by immunohistochemistry and mRNA expression of melanogenic markers (tyrosinase, tyrosinase-related protein-1 and MITF) by droplet digital PCR, while plasma levels of cytokines and chemokines were measured by a multiplex assay. In comparison with skin from healthy individuals, macular PKDL demonstrated a near total absence of Melan-A⁺ cells at dermal sites, while the polymorphic cases demonstrated a 3.2-fold decrease, along with a dramatic reduction in the expression of key enzymes related to the melanogenesis signalling pathway in both forms. The levels of circulating IFN-γ, IL-6, IL-2, IL-1β, TNF-α and IFN-γ-inducible chemokines (CXCL9/10/11) were elevated and was accompanied by an increased lesional infiltration of CD8⁺ T-cells. The proportion of CD8⁺ T-cells correlated strongly with plasma levels of IFN-γ (r = 0.8), IL-6 (r = 0.9, p < 0.05), IL-2 (r = 0.7), TNF-α (r = 0.9, p < 0.05) and IL-1β (r = 0.7), as also with CXCL9 (r = 0.5) and CXCL10 (r = 0.6). Taken together, the absence/reduction in Melan-A suggested hypopigmentation in PKDL was associated with the destruction of melanocytes, following the impairment of the melanogenesis pathway. Furthermore, the presence of CD8⁺ T-cells and an enhanced IFN-γ-associated immune milieu suggested the generation of a pro-inflammatory landscape that facilitated melanocyte dysfunction/destruction.

Post-Inflammatory Hypopigmentation: Review of the Etiology, Clinical Manifestations, and Treatment Options

Post-inflammatory hypopigmentation is a common acquired pigmentary disorder that is more prominent in skin of color, leading to great cosmetic and psychosocial implications. Often, a diagnosis with a pigmentary disorder can negatively impact an individual's health-related quality of life and may result in stigma. Although most cases of post-inflammatory hypopigmentation resolve spontaneously over time, a systematic diagnostic approach can help with identifying the underlying etiology and informing treatment strategies. It can be due to cutaneous inflammation, sequelae of inflammatory or infectious dermatoses, or dermatologic procedures. Therefore, a thorough understanding of the epidemiology, patient history, physical exam findings, and clinical features of post-inflammatory hypopigmentation phenomenon can explain the primary cause to providers and allow for patient education. It is also important to understand the various therapeutic approaches available and the efficacy of these options, which will inform providers to choose the appropriate therapy for patients. Although algorithms exist for classifying acquired disorders of hypopigmentation, there are no established algorithms for the diagnosis and treatment of post-inflammatory hypopigmentation, which warrants further exploration and discourse.

Extensive blaschkoid hypopigmentation in a girl with MED12-related disorder

MED12-related disorders represent a spectrum of rare neurodevelopmental disorders causing intellectual disability, dysmorphic features, and other systemic abnormalities. We report a case of a 21-month-old girl with extensive hypopigmentation following Blaschko lines attributed to underlying MED12-related disorder.

Vitiligo-like manifestations of graft-versus-host disease in a pediatric population

Vitiligo-like changes are an uncommon cutaneous manifestation of graft-versus-host disease (GVHD). We report three cases and review the literature of pediatric patients with vitiligo-like changes associated with GVHD. Improved characterization of this phenomenon may lend insight into the biologic pathways that underlie both vitiligo and GVHD.

Amyloidosis Cutis Dyschromica in a 16-Year-Old Filipino Girl: A Case Report

Amyloidosis cutis dyschromica is a rare variant of primary cutaneous amyloidosis characterized by hyper- and hypopigmented macules. In this paper, we reported a case of a 16-year-old Filipino girl with hyper- and hypopigmented to depigmented macules on the upper and lower extremities, which started when she was 9 years of age.

Oculo-Cutaneous Albinism Type 4 (OCA4): Phenotype-Genotype Correlation

Albinism is a genetic disorder, present worldwide, caused by mutations in genes affecting melanin production or transport in the skin, hair and eyes. To date, mutations in at least 20 different genes have been identified. Oculo-cutaneous Albinism type IV (OCA4) is the most frequent form in Asia but has been reported in all populations, including Europeans. Little is known about the genotype-phenotype correlation. We identified two main phenotypes via the analysis of 30 OCA4 patients with a molecularly proven diagnosis. The first, found in 20 patients, is clinically indistinguishable from the classical OCA1 phenotype. The genotype-to-phenotype correlation suggests that this phenotype is associated with homozygous or compound heterozygous nonsense or deletion variants with frameshift leading to translation interruption in the SLC45A2 gene. The second phenotype, found in 10 patients, is characterized by very mild hypopigmentation of the hair (light brown or even dark hair) and skin that is similar to the general population. In this group, visual acuity is variable, but it can be subnormal, foveal hypoplasia can be low grade or even normal, and nystagmus may be lacking. These mild to moderate phenotypes are associated with at least one missense mutation in SLC45A2.

Development of piperine nanoemulsions: an alternative topical application for hypopigmentation

In this study, it was aimed to develop a topical piperine nanoemulsion (P-NE) using an ultrasonic emulsification process to find an alternative treatment option for some hypopigmentation disorders such as vitiligo.Results showed that 150 mg piperine loaded NE with 1:2 oil phase to S_mix ratio and manufactured with 20 minutes ultrasonication duration with pre-emulsification step was the most durable formulation with a mean globule size of 216.00 ± 2.65, a PdI value of 0.094 ± 0.02 and a zeta potential value of -27.50 ± 2.48 mV.After three months of storage, the selected P-NE (coded as F3P2) remained kinetically stable without visual changes. This formulation displayed a sustained release pattern with a release of 81.92% ± 3.04% piperine after 72 hours. According to our in vitro activity experiments, it was determined that the P-NE had no toxic effect including dose of 5 mg/mL, and the highest P-NE formulation dose of 5 mg/mL increased tyrosinase activity by 32.77% ± 9.09% and melanogenesis activity by 34.90% ± 0.73%.In conclusion, it was demonstrated that the P-NE formulation may serve as a promising therapy for efficient treatment of vitiligo. Moreover, P-NE formulation may also help in preventing irregular pigmentation and skin cancer, associated with the conventional treatment methods.

Case Report: Wide Spectrum of Manifestations of Ligase IV Deficiency: Report of 3 Cases

DNA ligase IV deficiency is a rare autosomal recessive disorder associated with impaired DNA repair mechanisms. Most patients with DNA repair defects present with neurologic deficits, combined immunodeficiency, bone marrow failure, and/or hematologic neoplasia. We present 3 unrelated cases of ligase IV deficiency with different clinical presentations. Patient 1 presented at the age of 5 with bone marrow failure, dysmorphic features, and T and B lymphopenia. A compound heterozygous variant L19W/K635fs in the LIG4 gene was identified. Patient 2 presented at the age of 16 with recurrent infections. He had agammaglobulinemia and absent B cells. A homozygous R278H in the LIG4 gene was identified. Patient 3 was referred for vitiligo and B-cell lymphopenia (low class-switched B cells) and hypogammaglobulinemia. Homozygous R278H in LIG4 was also identified. In the last few years, the spectrum of clinical manifestations caused by ligase IV deficiency has widened, making it very difficult to establish an accurate clinical diagnosis. The use of NGS allows a proper diagnosis and provides a better prognosis and adequate family counseling.

Perifollicular Hypopigmentation in Systemic Sclerosis: Associations With Clinical Features and Internal Organ Involvement

OBJECTIVE

To determine whether perifollicular hypopigmentation in systemic sclerosis (SSc) is associated with demographics, distinct clinical features, and autoantibody profiles.

METHODS

Patients with SSc were prospectively enrolled, with a standardized data form used to collect anatomic distribution of perifollicular hypopigmentation. Associations between hypopigmentation and features of SSc were assessed.

RESULTS

Of 179 adult patients with SSc, 36 (20%) patients had perifollicular hypopigmentation. Of these 36 patients, 94% (n = 34) were female and 33% (n = 12) had limited cutaneous SSc. In univariable logistic regression, Black race (odds ratio [OR] 15.63, 95% CI 6.6-37.20, P < 0.001), diffuse cutaneous SSc (dcSSc; OR 4.62, 95% CI 2.11-10.09, P < 0.001), higher maximum modified Rodnan skin score (mRSS; OR 1.05, 95% CI 1.02-1.08, P = 0.003), myopathy (OR 3.92, 95% CI 1.80-8.57, P < 0.001), pulmonary fibrosis (OR 2.69, 95% CI 1.20-6.02, P = 0.02), lower minimum forced vital capacity % predicted (OR 0.96, 95% CI 0.94-0.99, P = 0.001), and lower minimum diffusing capacity for carbon monoxide % predicted (OR 0.97, 95% CI 0.95-0.99, P = 0.009) were associated with hypopigmentation. Anticentromere antibodies inversely associated with hypopigmentation (OR 0.24, 95% CI 0.07-0.86, P = 0.03). After adjusting for age, race, and disease duration, dcSSc (OR 4.28, 95% CI 1.46-12.53, P = 0.008) and increased mRSS (OR 1.07, 95% CI 1.02-1.12, P = 0.009) were significantly associated with hypopigmentation.

CONCLUSION

Perifollicular hypopigmentation is observed in a subset of patients with SSc and associated with diffuse subtype. Larger prospective studies determining whether perifollicular hypopigmentation precedes end-organ involvement and whether specific patterns associate with internal organ involvement are needed.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Facial hypopigmentation in skin of color: An atypical presentation of lichen nitidus

Lichen nitidus is a benign skin condition of unknown etiology that is classically described on the trunk, extremities, and genitalia as pinpoint flat-topped papules. In dark-skinned persons, the lesions may appear shiny or even hypopigmented. Lichen nitidus is less often described on the face. We describe a series of pediatric patients with skin of color who presented with the chief complaint of facial skin lightening and had associated clinical findings consistent with lichen nitidus.

Cutaneous findings in Fanconi anemia

BACKGROUND

Fanconi anemia (FA) is a genetic disorder that results in bone marrow failure, physical abnormalities, and solid organ malignancies. The diagnosis of FA is often delayed because the early disease characteristics have not been well established.

OBJECTIVE

To outline the spectrum of cutaneous findings seen in patients with FA.

METHODS

A cross-sectional study in which patients with FA received a full-body skin examination. Patient characteristics are summarized with mean (SD) for continuous and count (%) for categorical variables. Poisson regression and logistic regression models were used to examine the relationships between pigmentary changes and patient characteristics.

RESULTS

At least 1 cutaneous pigmentary alteration was present in 96.8% of patients, most arising before the teenage years. The most common finding was café-au-lait macules. Other findings included hypopigmented macules, skin-fold freckle-like macules, extensive sun-exposed freckling, and both hypopigmented and hyperpigmented pigment macules.

LIMITATIONS

Patients received a single assessment, so the number of pigmentary changes could not be assessed over time.

CONCLUSIONS

Characteristic morphology of FA includes faint and ill-defined café-au-lait macules, hypopigmented skin-fold freckle-like macules and the concurrence of hypopigmented and hyperpigmented macules. The recognition of these findings could aid clinicians in making earlier diagnoses.

Periorbital hypopigmentation and telangiectasias: Clues to diagnosing neonatal lupus in skin of color

Neonatal lupus erythematosus (NLE) is an autoimmune disease characterized by a periorbital erythematous rash. Although post-inflammatory hypopigmentation and telangiectasias are known possible sequelae, these features may be particularly noticeable in skin of color. Herein, we describe two infants with skin of color in whom periorbital hypopigmentation and telangiectasias were clues to the diagnosis of NLE.

A Novel Likely Pathogenic Variant in the BLOC1S5 Gene Associated with Hermansky-Pudlak Syndrome Type 11 and an Overview of Human BLOC-1 Deficiencies

Hermansky-Pudlak syndrome (HPS) is a heterogeneous disorder combining oculocutaneous albinism (OCA) and a platelet function disorder of varying severity as its most prominent features. The genes associated with HPS encode for different BLOC- (biogenesis of lysosome-related organelles complex) complexes and for the AP-3 (adaptor protein-3) complex, respectively. These proteins are involved in maturation, trafficking, and the function of lysosome-related organelles (LROs) such as melanosomes and platelet δ-granules. Some patients with different types of HPS can develop additional complications and symptoms like pulmonary fibrosis, granulomatous colitis, and immunodeficiency. A new type of HPS has recently been identified associated with genetic alterations in the BLOC1S5 gene, which encodes the subunit Muted of the BLOC-1 complex. Our aim was to unravel the genetic defect in two siblings with a suspected HPS diagnosis (because of OCA and bleeding symptoms) using next generation sequencing (NGS). Platelet functional analysis revealed reduced platelet aggregation after stimulation with ADP and a severe secretion defect in platelet δ-granules. NGS identified a novel homozygous essential splice site variant in the BLOC1S5 gene present in both affected siblings who are descendants of a consanguine marriage. The patients exhibited no additional symptoms. Our study confirms that pathogenic variants of BLOC1S5 cause the recently described HPS type 11.

A novel BLOC1S5-related HPS-11 patient and zebrafish with bloc1s5 disruption

Hermansky-Pudlak Syndrome (HPS) cases present with a variable degree of OCA and bleeding tendency. HPS is categorized into eleven types based on eleven causative genes, and disease severity varies among different types. By whole-exome sequencing performed on a family trio and Sanger sequencing of candidate variants, we identified a novel homozygous variant (NM_201280.3: c.181delC, p.Val61*) in BLOC1S5 in the patient who presents OCA and mild bleeding diathesis, and his healthy parents are heterozygous carriers. The variant can be considered pathogenic based on the guideline American College of Medical Genetics and Genomics, and the patient is proposed to be affected with HPS-11. In this study, we also explored bloc1s5 in zebrafish. bloc1s5 mRNA can be detected during early development of zebrafish. bloc1s5 knockdown zebrafish present with retinal hypopigmentation, thrombocytes loss and pericardial edema, and dll4/notch1 signaling and vascular integrity signaling are down-regulated at mRNA level in bloc1s5 morphants. The data from the first HPS-11 patient in Chinese population expand phenotypic and genotypic spectrum of HPS-11. Disruption of bloc1s5 in zebrafish recapitulates HPS-11-like phenotypes, and the potential signaling pathways associated with bloc1s5 are proposed. Altogether, this study may facilitate genetic counseling of HPS and investigation about BLOC1S5.

Prevalence of Hypopigmentary Disorders in Primary School Children in Zagazig City, Sharkia Governorate, Egypt

BACKGROUND

Epidemiologic data derived from population-based studies are very important to understand human diseases and their implications. Highlighting skin problems by identifying their incidence and prevalence is vital to direct suitable medical attention toward them.

AIM

The aim of the study was to detect the prevalence and most common causes of hypopigmentation in primary school children in Zagazig City.

METHODS

Cross-sectional study on 185 students selected from two schools. Data were collected by filling a questionnaire, clinical examination, and Wood's light examination to detect hypopigmented skin disorders.

RESULTS

The prevalence of hypopigmentation among studied population was 45.4%; the commonest cause was pityriasis alba 58.3%, followed by pityriasis versicolor 17.9%, postinflammatory hypopigmentation 10.7%, hypopigmented nevus 9.5%, and finally 3.6% vitiligo.

CONCLUSION

Hypopigmented skin disorders are important and easy to diagnosis skin diseases that need medical attention.

The link between hidradenitis suppurativa and phylloid hypomelanosis in partial trisomy-13 mosaicism: New evidences and further genetic/pathogenetic insights

Partial trisomy-13 mosaicism (PT13M) is a rare condition. Among its possible associated cutaneous features, phylloid hypomelanosis (PH), characterized by leaf-like macules reminiscent of floral ornaments in the form of round or oval spots and patches and oblong lesions, is typical. Two cases of PH associated with hidradenitis suppurativa (HS) have been already reported in the literature. We report a third child with PH due to PT13M associated with HS-like lesions limited to hypomelanotic regions. We hypothesize that follicular occlusion genes may be located in the duplicated part of chromosome 13.

Selective Cryolysis of Melanocytes: Critical Temperature and Exposure Time to Induce Selective Pigmentary Loss in Yucatan Pig Skin

BACKGROUND AND OBJECTIVES

Cryotherapy for melanocytic lesions is often accompanied by collateral damage to the surrounding skin, resulting in skin necrosis and scarring. Adipocytes, like melanocytes, are neural crest-derived cells. Adipocytes have been shown to be more sensitive to cold exposure than their neighboring cells of ectodermal origin, such as epidermal keratinocytes. Such differential sensitivity to cold exposure has led to the development of novel treatment modalities, like cryolipolysis, to selectively target a cell type while sparing neighboring cells.

STUDY DESIGN/MATERIALS AND METHODS

In this study, we investigated the roles of controlled skin freezing, tissue temperature, and exposure time in inducing selective loss of melanocytes and skin depigmentation in swines.

RESULTS

The results of our study demonstrated that contact cooling of the skin surface causes selective loss of epidermal melanocytes when the tissue temperature reaches -7.5°C or cooler with an exposure time of 10 minutes or longer, leading to partial skin depigmentation in swine skin. Longer exposures combined with colder temperature exposure led to more complete depigmentation in the treated skin surface.

CONCLUSION

Cold-sensitivity of melanocytes can be harnessed to selectively remove melanocytes while sparing surrounding keratinocytes. The results from this study demonstrated that improved clinical treatments specifically targeting melanocytic lesions is possible using skin cooling to achieve tissue temperatures capable of inducing selective loss of melanocytes without skin necrosis or scarring. Additional studies are needed to optimize the treatment conditions to prolong the selective removal of melanocytes. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Cutaneous granulomas as the presenting manifestation of Griscelli syndrome type 2

Griscelli syndrome type 2 is a rare autosomal recessive disorder characterized by hypopigmentation, silvery hair, and immunological dysfunction with no primary neurological impairment. We report an 18-month-old girl with Griscelli syndrome type 2 who presented to the dermatology department for cutaneous granulomas that developed following live-attenuated vaccination. Two compound heterozygous variants in the RAB27A gene were subsequently identified. She developed hemophagocytic lymphohistiocytosis, the key immunological concern, at age 5 years.

Vitiligo: An Updated Narrative Review

BACKGROUND

Vitiligo is a relatively common acquired pigmentation disorder that can cause significant psychological stress and stigmatism.

OBJECTIVE

This article aims to familiarize physicians with the clinical manifestations, evaluation, diagnosis, and management of vitiligo.

METHODS

A Pubmed search was conducted in Clinical Queries using the key term "vitiligo". The search included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English language. The information retrieved from the above search was used in the compilation of the present article.

RESULTS

Approximately one quarter of patients with vitiligo have the onset before 10 years of age. Genetic, immunological, neurogenic and environmental factors may have a role to play in the pathogenesis. Vitiligo typically presents as acquired depigmented, well-demarcated macules/patches that appear milk- or chalk-white in color. Lesions tend to increase in number and enlarge centrifugally in size with time. Sites of predilection include the face, followed by the neck, lower limbs, trunk, and upper limbs. The clinical course is generally unpredictable. In children with fair skin, no active treatment is usually necessary other than the use of sunscreens and camouflage cosmetics. If treatment is preferred for cosmesis, topical corticosteroids, topical calcineurin inhibitors, and narrowband ultraviolet B phototherapy are the mainstays of treatment.

CONCLUSION

The therapeutic effect of all the treatment modalities varies considerably from individual to individual. As such, treatment must be individualized. In general, the best treatment response is seen in younger patients, recent disease onset, darker skin types, and head and neck lesions. Topical corticosteroids and calcineurin inhibitors are the treatment choice for those with localized disease. Topical calcineurin inhibitors are generally preferred for lesions on genitalia, intertriginous areas, face, and neck. Narrowband ultraviolet B phototherapy should be considered in patients who have widespread vitiligo or those with localized vitiligo associated with a significant impact on the quality of life who do not respond to treatment with topical corticosteroids and calcineurin inhibitors.

Outcomes and adverse effects of ablative vs nonablative lasers for skin resurfacing: A systematic review of 1093 patients

It is generally believed that ablative laser therapies result in prolonged healing and greater adverse events when compared with nonablative lasers for skin resurfacing. To evaluate the efficacy of ablative laser use for skin resurfacing and adverse events as a consequence of treatment in comparison to other modalities, a PRISMA-compliant systematic review (Systematic Review Registration Number: 204016) of twelve electronic databases was conducted for the terms "ablative laser" and "skin resurfacing" from March 2002 until July 2020. Studies included meta-analyses, randomized control trials, cohort studies, and case reports to facilitate evaluation of the data. All articles were evaluated for bias. The search strategy produced 34 studies. Of 1093 patients included in the studies of interest, adverse events were reported in a total of 106 patients (9.7%). Higher rates of adverse events were described in nonablative therapies (12.2% ± 2.19%, 31 events) when compared with ablative therapy (8.28% ± 2.46%, 81 events). 147 patients (13.4%) reported no side effects, 68 (6.22%) reported expected, transient self-resolving events, and five (0.046%) presented with hypertrophic scarring. Excluding transient events, ablative lasers had fewer complications overall when compared with nonablative lasers (2.56% ± 2.19% vs 7.48% ± 3.29%). This systematic review suggests ablative laser use for skin resurfacing is a safe and effective modality to treat a range of pathologies from photodamage and acne scars to hidradenitis suppurativa and posttraumatic scarring from basal cell carcinoma excision. Further studies are needed, but these results suggest that ablative lasers are a superior, safe, and effective modality to treat damaged skin.

Cutaneous side effects in a cohort of patients with chronic myeloid leukemia treated with tyrosine kinase inhibitors: General description and further characterization, correlation with photoexposition and study of hypopigmentation as treatment's prognostic factor

Cutaneous adverse effects (AE) related to tyrosine-kinase inhibitor (TKI) drugs have been mainly described as case reports. We have characterized their appearance and correlation with patient's photoexposition habits and, further, with treatment response, in 61 patients with chronic myelogenous leukemia (CML) treated with TKI drugs. We have found hypopigmentation in 49.2% of the cases and a statistically significant association with interferon (IFN) intake. Eyelid edema's frequency was 45.4%. Mean photo-exposure was 1.95 h/day and only 8.3% of the patients used sunscreen daily. 44.3% of the patients reported a lighter skin color with the treatment and a statistically significant relationship with conjunctival hemorrhage was also found. Concordance between patients and dermatologist was moderate (kappa index 0.41). We found xerosis (21.3%), eczematous eruptions (21.3%), melasma (4.9%) and other isolated skin problems (ie, granulomatous panniculitis) in up to 16.4% of cases. Appearance of hypopigmented macules is associated to vascular conjunctival fragility and these patients need a slightly longer time to reach a complete molecular response, but without additional changes in survival or relapse frequency. We have stablished a specific dermatologic diagnosis in all the cases and we have not found the previously published as maculopapular rashes. Hypopigmentation, the more frequent AE, was not perceived as a relevant side effect. Photosensitivity, in our cases, was not reported, although imatinib-treated patients avoided sun-exposure. In addition, we identified some nonpreviously described dermatologic conditions in patients taking TKI drugs, like granulomatous panniculitis tufted folliculitis or oral spindle cell lipoma.

Restorative oncodermatology: Diagnosis and management of dermatologic sequelae from cancer therapies

The long-term survival of patients with cancer has risen dramatically during the last few decades. Despite this remarkable success, the same treatments that have enabled cure or remission often secondarily affect the skin, hair, and nails. Conditions including scarring, striae distensae, persistent alopecia, pigmentary changes, nail alterations, chronic radiation dermatitis, and radiation fibrosis have been associated with anxiety, depression, decreased quality of life, and impaired function. These dermatologic changes are cosmetically disfiguring, may limit activities, and are a visual reminder of past illness. Interventions toward improving these untoward sequelae and restoring the appearance and function of skin and appendages are critical for normalization and may contribute to improved quality of life in cancer survivors. Here, we outline dermatologic sequelae of cancer therapies with a review of medical and procedural treatment strategies to restore dermatologic health in the survivorship population.

Hypopigmented Mycosis Fungoides: Loss of Pigmentation Reflects Antitumor Immune Response in Young Patients

Hypopigmented mycosis fungoides (HMF) is a form of cutaneous T-cell lymphoma (CTCL), a heterogeneous group of extranodal non-Hodgkin's lymphomas. HMF has a unique set of defining features that include light colored to achromic lesions, a predilection for darker skin phototypes, an early onset of disease, and predominance of CD8⁺ T-cells, among others. In the current review, we detail the known pathways of molecular pathogenesis for this lymphoma and posit that an active Th1/cytotoxic antitumor immune response in part explains why this variant is primarily seen in children/adolescents and young adults, who do not exhibit signs of immunosenescence. As a result of this potent cytotoxic response, HMF patients experience mostly favorable overall prognosis, while hypopigmentation may in fact represent a useful surrogate marker of cytotoxic immunity targeting the malignant cells. Understanding the molecular processes behind the specific features that define HMF may lead to improved diagnostic accuracy, personalized prognosis by risk stratification, and improved management of HMF. Moreover, improving our knowledge of HMF may aid our further understanding of other cutaneous lymphomas.

Long-term survival in a cat with pancreatic adenocarcinoma treated with surgical resection and toceranib phosphate

Case summary

Primary pancreatic adenocarcinoma is an uncommon neoplasm seen in cats and often has a poor prognosis. We report a case of an 8-year-old male neutered domestic shorthair cat weighing 5.8 kg diagnosed with pancreatic adenocarcinoma treated with surgical resection and toceranib phosphate, which had a progression-free interval of 1148 days and survived for more than 1436 days. The treatment was well tolerated; however, the cat developed generalised coat hypopigmentation.

Relevance and novel information

To our knowledge, the cat in our report has the longest progression-free interval and survival time post-surgical resection of pancreatic carcinoma treated with toceranib. Hypopigmentation as a side effect of toceranib has been reported in dogs, but this is the first case reported in cats.

Molecular characterization of SLC24A5 variants and evaluation of Nitisinone treatment efficacy in a zebrafish model of OCA6

Skin pigmentation is a highly heterogeneous trait with diverse consequences worldwide. SLC24A5, encoding a potent K⁺ -dependent Na⁺ /Ca²⁺ exchanger, is among the known color-coding genes that participate in melanogenesis by maintaining pH in melanosomes. Deficient SLC24A5 activity results in oculocutaneous albinism (OCA) type 6 in humans. In this study, by utilizing a exome sequencing (ES) approach, we identified two new variants [p. (Gly110Arg) and p. (IIe189Ilefs*1)] of SLC24A5 cosegregating with the OCA phenotype, including nystagmus, strabismus, foveal hypoplasia, albinotic fundus, and vision impairment, in three large consanguineous Pakistani families. Both of these variants failed to rescue the pigmentation in zebrafish slc24a5 morphants, confirming the pathogenic effects of the variants. We also phenotypically characterized a commercially available zebrafish mutant line (slc24a5^ko ) that harbors a nonsense (p.Tyr208*) allele of slc24a5. Similar to morphants, homozygous slc24a5^ko mutants had significantly reduced melanin content and pigmentation. Next, we used these slc24a5^ko zebrafish mutants to test the efficacy of nitisinone, a compound known to increase ocular and fur pigmentation in OCA1 (TYR) mutant mice. Treatment of slc24a5^ko mutant zebrafish embryos with varying doses of nitisinone did not improve melanin production and pigmentation, suggesting that treatment with nitisinone is unlikely to be therapeutic in OCA6 patients.