Dissolution or degeneration of bone tissue of the phalanges of the hand.

The X-linked otopalatodigital (X-OPD) spectrum disorders, characterized primarily by skeletal dysplasia, include the following: Otopalatodigital syndrome type 1 (OPD1). Otopalatodigital syndrome type 2 (OPD2). Frontometaphyseal dysplasia type 1 (FMD1). Melnick-Needles syndrome (MNS). Terminal osseous dysplasia with pigmentary skin defects (TODPD). In OPD1, most manifestations are present at birth; females can present with severity similar to affected males, although some have only mild manifestations. In OPD2, females are less severely affected than related affected males. Most males with OPD2 die during the first year of life, usually from thoracic hypoplasia resulting in pulmonary insufficiency. Males who live beyond the first year of life are usually developmentally delayed and require respiratory support and assistance with feeding. In FMD1, females are less severely affected than related affected males. Males do not experience a progressive skeletal dysplasia but may have joint contractures and hand and foot malformations. Progressive scoliosis is observed in both affected males and females. In MNS, wide phenotypic variability is observed; some individuals are diagnosed in adulthood, while others require respiratory support and have reduced longevity. MNS in males results in perinatal lethality in all recorded cases. TODPD, seen only in females, is characterized by a skeletal dysplasia that is most prominent in the digits, pigmentary defects of the skin, and recurrent digital fibromata.

The spectrum of ASAH1-related disorders ranges from Farber disease (FD) to spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). Classic FD is characterized by onset in the first weeks of life of painful, progressive deformity of the major joints; palpable subcutaneous nodules of joints and mechanical pressure points; and a hoarse cry resulting from granulomas of the larynx and epiglottis. Life expectancy is usually less than two years. In the other less common types of FD, onset, severity, and primary manifestations vary. SMA-PME is characterized by early-childhood-onset progressive lower motor neuron disease manifest typically between ages three and seven years as proximal lower-extremity weakness, followed by progressive myoclonic and atonic seizures, tremulousness/tremor, and sensorineural hearing loss. Myoclonic epilepsy typically begins in late childhood after the onset of weakness and can include jerking of the upper limbs, action myoclonus, myoclonic status, and eyelid myoclonus. Other findings include generalized tremor, and cognitive decline. The time from disease onset to death from respiratory complications is usually five to 15 years.

Vascular Ehlers-Danlos syndrome (vEDS) is characterized by arterial, intestinal, and/or uterine fragility; thin, translucent skin; easy bruising; characteristic facial appearance (thin vermilion of the lips, micrognathia, narrow nose, prominent eyes); and an aged appearance to the extremities, particularly the hands. Vascular dissection or rupture, gastrointestinal perforation, or organ rupture are the presenting signs in most adults with vEDS. Arterial rupture may be preceded by aneurysm, arteriovenous fistulae, or dissection but also may occur spontaneously. The majority (60%) of individuals with vEDS who are diagnosed before age 18 years are identified because of a positive family history. Neonates may present with clubfoot, hip dislocation, limb deficiency, and/or amniotic bands. Approximately half of children tested for vEDS in the absence of a positive family history present with a major complication at an average age of 11 years. Four minor diagnostic features – distal joint hypermobility, easy bruising, thin skin, and clubfeet – are most often present in those children ascertained without a major complication.

Hajdu-Cheney syndrome (HJCYS) is a rare autosomal dominant skeletal disorder characterized by short stature, coarse and dysmorphic facies, bowing of the long bones, and vertebral anomalies. Facial features include hypertelorism, bushy eyebrows, micrognathia, small mouth with dental anomalies, low-set ears, and short neck. There is progressive focal bone destruction, including acroosteolysis and generalized osteoporosis. Additional and variable features include hearing loss, renal cysts, and cardiovascular anomalies (summary by Ramos et al., 1998; Simpson et al., 2011; Isidor et al., 2011).

Dissolution or degeneration of bone tissue of the phalanges of the hand.

Satoyoshi syndrome is a rare disorder characterized by progressive, painful, intermittent muscle spasms, diarrhea or unusual malabsorption, endocrinopathy with amenorrhea, and secondary skeletal abnormalities. The disorder is also called komuragaeri disease by the Japanese; in Japanese 'komura' means calf and 'gaeri' means 'turnover' or spasm. All cases have apparently been sporadic, even when occurring in large families (Ehlayel and Lacassie, 1995).

Mitochondrial DNA (mtDNA)-associated Leigh syndrome and NARP (neurogenic muscle weakness, ataxia, and retinitis pigmentosa) are part of a continuum of progressive neurodegenerative disorders caused by abnormalities of mitochondrial energy generation. Leigh syndrome (or subacute necrotizing encephalomyelopathy) is characterized by onset of symptoms typically between ages three and 12 months, often following a viral infection. Decompensation (often with elevated lactate levels in blood and/or CSF) during an intercurrent illness is typically associated with psychomotor retardation or regression. Neurologic features include hypotonia, spasticity, movement disorders (including chorea), cerebellar ataxia, and peripheral neuropathy. Extraneurologic manifestations may include hypertrophic cardiomyopathy. About 50% of affected individuals die by age three years, most often as a result of respiratory or cardiac failure. NARP is characterized by proximal neurogenic muscle weakness with sensory neuropathy, ataxia, and pigmentary retinopathy. Onset of symptoms, particularly ataxia and learning difficulties, is often in early childhood. Individuals with NARP can be relatively stable for many years, but may suffer episodic deterioration, often in association with viral illnesses.

Haim-Munk syndrome is an autosomal recessive disorder characterized by palmoplantar keratoderma, severe periodonitis, arachnodactyly, acroosteolysis, atrophic changes of the nails, and a radiographic deformity of the fingers (summary by Hart et al., 2000).

Hereditary sensory and autonomic neuropathy type II (HSAN2) is characterized by progressively reduced sensation to pain, temperature, and touch. Onset can be at birth and is often before puberty. The sensory deficit is predominantly distal with the lower limbs more severely affected than the upper limbs. Over time sensory function becomes severely reduced. Unnoticed injuries and neuropathic skin promote ulcerations and infections that result in spontaneous amputation of digits or the need for surgical amputation. Osteomyelitis is common. Painless fractures can complicate the disease. Autonomic disturbances are variable and can include hyperhidrosis, tonic pupils, and urinary incontinence in those with more advanced disease.

Hereditary sensory and autonomic neuropathy type II (HSAN2) is characterized by progressively reduced sensation to pain, temperature, and touch. Onset can be at birth and is often before puberty. The sensory deficit is predominantly distal with the lower limbs more severely affected than the upper limbs. Over time sensory function becomes severely reduced. Unnoticed injuries and neuropathic skin promote ulcerations and infections that result in spontaneous amputation of digits or the need for surgical amputation. Osteomyelitis is common. Painless fractures can complicate the disease. Autonomic disturbances are variable and can include hyperhidrosis, tonic pupils, and urinary incontinence in those with more advanced disease.

Hereditary sensory neuropathy type IF is an autosomal dominant sensory neuropathy affecting the lower limbs. Distal sensory impairment becomes apparent during the second or third decade of life, resulting in painless ulceration of the feet with poor healing, which can progress to osteomyelitis, bone destruction, and amputation. There is no autonomic involvement, spasticity, or cognitive impairment (summary by Kornak et al., 2014). For a discussion of genetic heterogeneity of HSN, see HSAN1A (162400).

Singleton-Merten syndrome-2 is characterized by variable expression of glaucoma, aortic calcification, and skeletal abnormalities, without dental anomalies (summary by Jang et al., 2015). For a general phenotypic description and discussion of genetic heterogeneity of Singleton-Merten syndrome, see SGMRT1 (182250).

Singleton-Merten syndrome (SGMRT) is an uncommon autosomal dominant disorder characterized by abnormalities of blood vessels, teeth, and bone. Calcifications of the aorta and aortic and mitral valves occur in childhood or puberty and can lead to early death. Dental findings include delayed primary tooth exfoliation and permanent tooth eruption, truncated tooth root formation, early-onset periodontal disease, and severe root and alveolar bone resorption associated with dysregulated mineralization, leading to tooth loss. Osseous features consist of osteoporosis, either generalized or limited to distal extremities, distal limb osteolysis, widened medullary cavities, and easy tearing of tendons from bone. Less common features are mild facial dysmorphism (high anterior hair line, broad forehead, smooth philtrum, thin upper vermilion border), generalized muscle weakness, psoriasis, early-onset glaucoma, and recurrent infections. The disorder manifests with variable inter- and intrafamilial phenotypes (summary by Rutsch et al., 2015). Genetic Heterogeneity of Singleton-Merten Syndrome An atypical form of Singleton-Merten syndrome (SGMRT2; 616298) is caused by mutation in the DDX58 gene (609631) on chromosome 9p21.

Autosomal recessive primary hypertrophic osteoarthropathy-1 (PHOAR1) is a rare familial disorder characterized by digital clubbing, osteoarthropathy, and acroosteolysis, with variable features of pachydermia, delayed closure of the fontanels, and congenital heart disease (summary by Uppal et al., 2008; Radhakrishnan et al., 2020). Secondary hypertrophic osteoarthropathy, or pulmonary hypertrophic osteoarthropathy, is a different disorder characterized by digital clubbing secondary to acquired diseases, most commonly intrathoracic neoplasm (Uppal et al., 2008). Touraine et al. (1935) recognized pachydermoperiostosis as a familial disorder with 3 clinical presentations or forms: a complete form characterized by periostosis and pachydermia; an incomplete form with bone changes but without pachydermia; and a 'forme fruste' with pachydermia and minimal skeletal changes. Genetic Heterogeneity Autosomal recessive primary hypertrophic osteoarthropathy-2-enteropathy syndrome (PHOAR2E; 614441) is caused by mutation in the SLCO2A1 gene (601460) on chromosome 3q22. Families with an autosomal dominant form of primary hypertrophic osteoarthropathy have also been reported (PHOAD; 167100).

Warburg-Cinotti syndrome (WRCN) is characterized by progressive corneal neovascularization, keloid formation, chronic skin ulcers, wasting of subcutaneous tissue, flexion contractures of the fingers, and acroosteolysis (Xu et al., 2018).

Mandibuloacral dysplasia progeroid syndrome (MDPS) is an autosomal recessive severe laminopathy-like disorder characterized by growth retardation, bone resorption, arterial calcification, renal glomerulosclerosis, and hypertension (Elouej et al., 2020).