A rare, genetic, hyperpigmentation of the skin disease characterized by childhood to adulthood-onset of reticulate, slightly depressed, sharply demarcated, brown, macular skin lesions without hypopigmentation, affecting the dorsa of the hands and feet, and, occasionally, progressing to involve limbs, neck, forehead and/or trunk. Interrupted dermatoglyphics and palmoplantar pits may be additionally observed. Histologically, hyperpigmented lesions show slightly elongated and thinned rete ridges, mild hyperkeratosis without parakeratosis and absence of incontinentia pigmenti.

Schimke immunoosseous dysplasia (SIOD) is characterized by spondyloepiphyseal dysplasia (SED) resulting in short stature, nephropathy, and T cell deficiency. Radiographic manifestations of SED include ovoid and mildly flattened vertebral bodies, small ilia with shallow dysplastic acetabular fossae, and small deformed capital femoral epiphyses. Nearly all affected individuals have progressive steroid-resistant nephropathy, usually developing within five years of the diagnosis of growth failure and terminating with end-stage renal disease. The majority of tested individuals have T cell deficiency and an associated risk for opportunistic infection, a common cause of death. SIOD involves a spectrum that ranges from an infantile or severe early-onset form with a greater risk of death during childhood to a juvenile or milder later-onset form with likely survival into adulthood if renal disease is appropriately treated.