Ultrastructural lipid and glycoconjugate cytochemistry of membranous lipodystrophy (Nasu-Hakola disease)

The Primary Microglial Leukodystrophies: A Review

Primary microglial leukodystrophy or leukoencephalopathy are disorders in which a genetic defect linked to microglia causes cerebral white matter damage. Pigmented orthochromatic leukodystrophy, adult-onset orthochromatic leukodystrophy associated with pigmented macrophages, hereditary diffuse leukoencephalopathy with (axonal) spheroids, and adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) are different terms apparently used to designate the same disease. However, ALSP linked to dominantly inherited mutations in CSF1R (colony stimulating factor receptor 1) cause CSF-1R-related leukoencephalopathy (CRP). Yet, recessive ALSP with ovarian failure linked to AARS2 (alanyl-transfer (t)RNA synthase 2) mutations (LKENP) is a mitochondrial disease and not a primary microglial leukoencephalopathy. Polycystic membranous lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL; Nasu–Hakola disease: NHD) is a systemic disease affecting bones, cerebral white matter, selected grey nuclei, and adipose tissue The disease is caused by mutations of one of the two genes TYROBP or TREM2, identified as PLOSL1 and PLOSL2, respectively. TYROBP associates with receptors expressed in NK cells, B and T lymphocytes, dendritic cells, monocytes, macrophages, and microglia. TREM2 encodes the protein TREM2 (triggering receptor expressed on myeloid cells 2), which forms a receptor signalling complex with TYROBP in macrophages and dendritic cells. Rather than pure microglial leukoencephalopathy, NHD can be considered a multisystemic “immunological” disease.

Lipomembranous changes associated with systemic lupus erythematosus

Lipomembranous changes are distinctive histopathological findings, which include the presence of cystic cavities lined by crenulated, hyaline membranes in adipose tissue. It is likely that ischaemia is fundamental to the development of these lesions, and that lipomembranes are formed from the products of degenerating fat cell membranes by some unknown mechanism. Such changes may be seen, although rarely, in many types of subcutaneous inflammatory processes. However, an association with systemic lupus erythematosus (SLE) is rare. We report a patient with SLE who had the histological features of lipomembranous changes associated with vasculopathy.

Myeloid DAP12-associating lectin (MDL)-1 regulates synovial inflammation and bone erosion associated with autoimmune arthritis

DNAX adaptor protein 12 (DAP12) is a trans-membrane adaptor molecule that transduces activating signals in NK and myeloid cells. Absence of functional Dap12 results in osteoclast defects and bone abnormalities. Because DAP12 has no extracelluar binding domains, it must pair with cell surface receptors for signal transduction. There are at least 15 known DAP12-associating cell surface receptors with distinct temporal and cell type-specific expression patterns. Our aim was to determine which receptors may be important in DAP12-associated bone pathologies. Here, we identify myeloid DAP12-associating lectin (MDL)-1 receptor (also known as CLEC5A) as a key regulator of synovial injury and bone erosion during autoimmune joint inflammation. Activation of MDL-1 leads to enhanced recruitment of inflammatory macrophages and neutrophils to the joint and promotes bone erosion. Functional blockade of MDL-1 receptor via Mdl1 deletion or treatment with MDL-1-Ig fusion protein reduces the clinical signs of autoimmune joint inflammation. These findings suggest that MDL-1 receptor may be a therapeutic target for treatment of immune-mediated skeletal disorders.

[Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy]

A 32-year-old patient presented with presenile dementia syndrome and complex-partial seizures. The dementia was preceded by recurrent bone pain which led to surgical intervention for ossear cysts. Computed tomography revealed intracerebral calcification and marked brain atrophy. Clinical, radiological, genetic, and histopathological features of PLOSL disease are discussed in the differential diagnosis of presenile dementia and basal ganglia calcification.

Unilateral necrobiosis lipoidica of the ischemic limb--a case report

A 63-year-old diabetic woman presented with new-onset intermittent claudication of the right calf accompanied by ipsilateral necrobiosis lipoidica (NL). The latter presented the typical appearance of oval, indurated plaques, with brownish-red margins and central atrophy, scattered over the right thigh and calf. Arteriography demonstrated severe obstructive lesions on the right femoral artery. NL and claudication spared the left leg. A possible ischemic pathogenesis of NL emerges from this observation and is supported by recent studies in the literature.

Nasu-Hakola disease: a review of its leukoencephalopathic and membranolipodystrophic features

The clinicopathological features of Nasu-Hakola disease are described by reviewing previously reported cases and adding consideration to newly disclosed evidence. This disease is an autosomal recessive disorder characterized by membranocystic lipodystrophy in the skeletal system and sclerosing leukoencephalopathy in the nervous system. The leukoencephalopathic alterations are demyelinization of the cerebral white matter, associated with conspicuous fibrillary gliosis and preservation of the subcortical arcuate fibers. Sudanophilic granules are focally scattered in the perivascular space or widely infiltrated in the affected white matter, and some neuronal loss with deposits of calcospherites is encountered in the basal ganglia and also in the thalamus. Spheroid formation with an increased number of neurofilaments in the neuronal axon is considered a possible pathogenesis, and a primary vascular mechanism is also suggested. Interestingly, most of the reported cases of Nasu-Hakola disease are from Japan and Finland which suggests heredofamilial background as a cause.

Nasu-Hakola syndrome: polycystic lipomembranous osteodysplasia with sclerosing leucoencephalopathy and presenile dementia

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Panniculitis: recent developments and observations

Dermatopathologists rarely greet a biopsy of panniculitis with total confidence that a specific, definitive diagnosis will be rendered. As with many other areas in dermatopathology, our understanding of the pathogenesis of many forms of panniculitis is incomplete. This article examines a subset of panniculitis primarily from a pathogenetic standpoint, with the intention of providing a differential diagnosis for those cases in which ischemic changes are seen in the subcutis. The diverse group of conditions evoked by this approach also shares the distinction of having been the focus of nosologic and causative controversy, both historically and currently. In particular, stasis-associated sclerosing panniculitis, vascular calcification-cutaneous necrosis syndrome (calciphylaxis), oxalosis, and nodular vasculitis-erythema induratum are examined in depth. Erythema nodosum and variants, other granulomatous panniculitides, and panniculitides showing cytophagocytosis are also discussed with current perspectives.

Lipomembranous (membranocystic) fat necrosis. Clinicopathologic correlation of 38 cases

Clinicopathologic correlation of cutaneous biopsy specimens demonstrating typical lipomembranous fat necrosis was performed. Material from 732 biopsies of various subcutaneous inflammatory disorders seen at our institution in the past 5 years was screened for typical lipomembranous (membranocystic) changes in the panniculus, and 39 specimens from 38 patients with these changes were identified. The most common clinical context in which this condition was observed was in chronic sclerotic plaques of the lower legs associated with venous insufficiency (37% of the total cases). All patients were women, and the majority were obese. Typical lipomembranous fat necrosis was also observed in eight cases (21%) of erythema nodosum, three (8%) of morphea or subcutaneous morphea (or both), two (5%) of lupus panniculitis, two (5%) of necrobiosis lipoidica, and in single cases of polyarteritis nodosa, necrotizing vasculitis, and erysipelas. Six cases (16%) had no definite underlying disease. The mean age of all patients was 57 years (range 32-86 years), and 34 patients (89%) were women. Of the five major categories identified, lipomembranes lining macrocysts and microcysts were most prominent in the venous insufficiency- and morphea-related cases and were much less prominent in erythema nodosum, lupus panniculitis, and necrobiosis lipoidica, which generally showed histopathologic findings typical of these disorders. In addition to lining the macrocystic and microcystic cavities formed in the fat lobules, lipomembranes were prominent in areas of septal fibrosis in all cases associated with morphea and necrobiosis lipoidica and in 35% and 25% of venous insufficiency- and erythema nodosum-related cases, respectively. In lupus panniculitis, lipomembranes were most prominent in areas of hyaline necrosis. We conclude that lipomembranous fat necrosis is most likely a nonspecific form of ischemic fat degeneration that may be induced by various clinical entities. This change is most often seen in venous insufficiency-associated chronic sclerotic plaques typically observed in middle-aged obese women, and we propose the term stasis-associated lipomembranous panniculitis (SALP) to describe this most common form of lipomembranous fat necrosis.

Lipomembranous (membranocystic) changes associated with morphea: a clinicopathologic review of three cases

Lipomembranous (membranocystic) changes represent a distinctive form of pathology in adipose tissue. Although first described in the rare neurodegenerative disorder now called Nasu-Hakola disease, this change has also been observed in a variety of relatively common inflammatory and noninflammatory dermatoses. We report three cases of morphea associated with marked lipomembranous (membranocystic) changes in the subcutaneous adipose tissue.