Discuss the differential diagnosis of photodermatoses in infants or young children.

In the neonatal period, photodermatoses are uncommon, probably due in part to the minimal degree of exposure to sunlight. However, cutaneous lesions of neonatal lupus erythematosus typically occur very early in life and are often photoexacerbated. These patients develop erythematous, often annular plaques, usually distributed on the face and scalp. Cardiac conduction defects may also be seen. Nearly all of these infants and their mothers have circulating anti–Ro/SS-A antibodies and, less commonly, anti–La/SS-B antibodies. The differential diagnosis also includes several genodermatoses that may present as photosensitivity early in life. Other childhood photodermatoses include polymorphous light eruption, photodrug eruptions, photocontact dermatitis, hydroa aestivale, hydroa vacciniforme, erythropoietic protoporphyria, and cutaneous lupus erythematosus (Table 17-3).

 

Table 17-3. Genodermatoses Associated with Photosensitivity
	DISEASE		SKIN FINDINGS		INHERITANCE		OTHER
	Xeroderma pigmentosum		Lentigines, skin cancers, photoaging		Autosomal recessive		Photophobia, keratitis, corneal opacification and vascularization, neurologic abnormalities: hyporeflexia, deafness, seizures (most common in groups A and D; do not usually occur in XP variant). XP variant patients usually have no neurologic problems. Complementation groups A to G: defective global genomic nucleotide excision repair (GG-NER) of UVRinduced DNA damage (e.g., pyrimidine dimers) from any part of the genome
	Cockayne’s syndrome		Photosensitivity without pigmentary changes or increased risk of skin cancer. Scaly facial photodermatitis		Autosomal recessive		Loss of adipose tissue, prominent ears, dental caries, thinning of skin and hair. Hypogonadism, stooped posture, joint contractures, short stature with extremely thin body habitus (“cachectic dwarfism”), microcephaly, mental retardation, deafness. Calcification of basal ganglia, demyelination, pigmentary retinal degeneration, osteoporosis. Cockayne’s syndrome (CS) cells are defective in the repair of pyrimidine dimer photoproducts and oxidative DNA base modifications typically induced by UVB and UVA, respectively. Two complementation groups: CS-A (mutations in ERCC8) and CS-B (mutations in ERCC6); identical phenotypes. Mutations in XPB, XPD, and XPG genes have been associated with combined XP/CS phenotypes
	Trichothiodystrophy		Ichthyosis, brittle hair. Hair shaft: alternating light and dark bands (“tiger tail banding”), trichoschisis, trichorrhexis nodosa		Autosomal recessive		PIBI(D)S: photosensitivity, ichthyosis, brittle hair, intellectual impairment, decreased fertility, short stature. Other features: microcephaly, receding chin, protruding ears. Mutations in XPD, XPB, general transcription factor IIH polypeptide 5 (GTF2H5 or TFB5), and C7orf11
	UV-sensitive syndrome (UVsS)		Photosensitivity, solar lentigines		Autosomal recessive		Similar to CS: defective TC-NER, normal GG-NER; however, unlike CS, patients with UVsS only have defective in repair of UVB-induced photoproducts (not repair of oxidative damage). Two complementation groups: mutations in ERCC6, and an undefined gene.
	Bloom’s syndrome		Malar erythema and telangiectasias, café-au-lait macules, hypopigmentation		Autosomal recessive		Elongated face with malar hypoplasia and prominent nose, short stature, diabetes mellitus, recurrent infections. Small at birth, severe growth retardation, respiratory infections, malignancy. Increased frequency of leukemia, lymphoma, GI adenocarcinoma. Men: sterile; women: reduced fertility. Normal intelligence. Decreased IgA, IgM, sometimes IgG. Mutations in BLM (RECQL3), resulting in chromosomal instability (increased sister chromatid exchanges, chromosomal breakage and rearrangement). Quadriradial configurations in lymphocytes and fibroblasts are diagnostic.
	Rothmund- Thomson syndrome		Erythema, edema and vesicles on the cheeks and face during the first few months of life, followed by poikiloderma that also typically affects the dorsal aspect of the hands/forearms and the buttocks. Sparse hair (scalp, eyebrows, eyelashes), hypoplastic nails, acral keratoses (in adolescents and adults)		Autosomal recessive syndrome		Cataracts, usually normal intelligence, and cerebellar ataxia. Short stature, skeletal (e.g., radial ray defects, osteoporosis) and dental abnormalities, juvenile cataracts, chronic diarrhea/ vomiting during infancy, pituitary hypogonadism (may be associated with midface hypoplasia/ “saddle nose”). Osteosarcoma (10%230%), squamous cell carcinoma (,5%; often acral). Normal immune function, intelligence, and lifespan (in the absence of malignancy). Mutations in RECQL4; protein product is a DNA helicase. Genomic instability may account for propensity for malignancies.
	Hartnup’s disease		Pellagra-like eruption		Autosomal recessive		Intermittent ataxia, which may be accompanied by nystagmus and tremors. Psychiatric disturbances and other nonspecific neurologic abnormalities have been reported in some patients, but significant mental retardation is not a feature. Defective renal and intestinal neutral amino acid transport. Marked aminoaciduria and tryptophan deficiency.
	Kindler syndrome		Poikiloderma, trauma-induced skin blistering, mucosal inflammation		Autosomal recessive		Subtype of epidermolysis bullosa (EB). Loss-of-function mutations in the gene. Clinical overlap between Kindler syndFERMT1rome and dystrophic EB. Unlike other forms of EB, Kindler syndrome is characterized by impaired actin cytoskeleton-extracellular matrix interactions and a variable plane of blister formation at or close to the dermal–epidermal junction.